This invention relates generally to control systems for gas turbine engines, and, more particularly, to methods and apparatus for estimating governor dynamics.
Gas turbine engines typically include a governing sub-system that maintains the gas turbine engine at a pre-determined operational speed. For example, in a helicopter including a main rotor, the governing sub-system facilitates improving handling qualities of the helicopter. More specifically, the governing sub-system attempts to maintain the helicopter main rotor speed, NR, at a reference value, NR_REF, despite being subjected to external disturbances such as actions from pedal and cyclic, air speeds, and wind gust. FIG. 1 illustrates the overall helicopter engine control with a Full Authority Digital Engine Control (FADEC). The helicopter can change the load in the rotor system by collective pitch (CLP), cyclic, and pedals. When load is increased the rotor speed decreases, the governing system in FADEC can react to the changes in the main rotor speed, NR based on measured engine parameters and rotor speed and increase fuel flow (WF).
To improve operational handling qualities, feed forward anticipation signals may be used by the governing system to anticipate and correct for transients. If feed forward anticipation signals are not active for some maneuvers, the main rotor speed is maintained by an isochronous gas turbine Np governor, and the helicopter system responsiveness and disturbance rejection capability are reliant upon only the governor dynamics within the governing sub-system.
Known governing sub-systems use relatively simple lead-lag compensation to attenuate the main rotor response to facilitate a stable system. In addition, notch filters, centered at main rotor resonance, are often included to permit higher system frequency crossover and improved phase margin for the governing sub-system. However, these methods do not directly address system disturbance rejection capability. Furthermore, the simple structure of the governor dynamics may yield a low bandwidth system, thus limiting an overall system performance.
In one aspect of the invention, a method for estimating gas turbine engine governor dynamics within a system is provided. The gas turbine engine includes a plurality of sensors responsive to engine operations. The method comprises identifying a first set of parameters utilized in the governing system, identifying a second set of parameters utilized in the governing system, and generating governor dynamics estimates utilizing the first and second sets of parameters to solve multiple objective optimization algorithms.
In another aspect, an apparatus for estimating governor dynamics for a gas turbine engine used in a system is provided. The apparatus is programmed to obtain a first set of parameters from a governing sub-system coupled to the system, obtain a second set of parameters from the governing sub-system, and generate governor dynamics estimates utilizing the first and second sets of parameters to solve multiple objective optimization algorithms.
In a further aspect of the invention, a governor dynamics estimation process for a system including a gas turbine engine is provided. A governor is coupled to the engine, and the design process utilizes a processor. The processor is configured to receive a first set of parameter outputs indicative of system responsiveness, receive a second set of parameter outputs indicative of system stability robustness, and generate governor estimates utilizing the first and second sets of parameters to solve multiple objective optimization algorithms.